What's new in atopic eczema? An analysis of systematic reviews published in 2016. Part 2: Epidemiology, aetiology and risk factors.

This review forms part of a series of annual updates that summarize the evidence base for atopic eczema (AE), providing a succinct guide for clinicians and patients. It presents the key findings from 14 systematic reviews published in 2016, focusing on AE epidemiology, aetiology and risk factors. For systematic reviews on the treatment and prevention of AE and for nomenclature and outcome assessments, see Parts 1 and 3 of this update, respectively. The annual self-reported prevalence of AE is a range of 11.4-24.2%, compared with a general practioner-diagnosed prevalence of 1.8-9.5%. The mean age of AE diagnosis is 1.6 years. Persistent AE is associated with more severe disease at the time of diagnosis, onset after the age of 2 years and female sex. There is a significant association between having AE and subsequent development of food allergy. Food allergy is also associated with more severe and persistent AE. No consistent association was found between the timing of allergenic food introduction and the risk of developing AE. Evidence from heterogeneous studies indicates that skin absorption is increased in patients with AE, and that there is increased colonization with Staphylococcus aureus in lesional and nonlesional skin and the nasal mucosa of patients with AE compared with controls. There is uncertain evidence indicating an association between AE and smoking exposure, antenatal infection and low maternal vitamin D levels during pregnancy. Weak evidence suggests an increased risk of basal cell carcinoma, but not of melanoma or squamous cell carcinoma, while the risk of glioma is reduced.